Quarterly report pursuant to Section 13 or 15(d)

EMPLOYEE BENEFIT PLANS - Additional Information (Detail)

v3.21.2
EMPLOYEE BENEFIT PLANS - Additional Information (Detail)
$ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Apr. 30, 2021
USD ($)
Dec. 31, 2007
USD ($)
Jun. 30, 2021
USD ($)
Sep. 30, 2021
USD ($)
employee
Dec. 31, 2020
USD ($)
employee
Defined Benefit Plan Disclosure [Line Items]          
Defined benefit plan, net actuarial gain (loss) $ 2,100        
Actuarial gain (loss) 3,700        
Basis point increase       0.49%  
Benefit related to workforce reductions 100        
Asset loss resulting from actual asset returns $ 1,700        
Basis points below our expected return 4.30%        
Actuarial gain recorded in accumulated other comprehensive income $ 2,100        
Pre-tax actuarial gain     $ 69    
Actuarial gain, after tax     52    
Multiemployer Plans, Payment Term       41 years  
Other Comprehensive Income (Loss), Defined Benefit Plan, Plan Amendments, Reclassification Adjustment from AOCI, before Tax     66    
Other Comprehensive Income (Loss), Defined Benefit Plan, Plan Amendments, Reclassification Adjustment from AOCI, After Tax     $ 50    
National Master Agreement And Various Supplemental Agreements          
Defined Benefit Plan Disclosure [Line Items]          
Number of employees covered | employee       316,000  
Independent Pilots Association          
Defined Benefit Plan Disclosure [Line Items]          
Number of employees covered | employee         3,000
Teamsters Local 2727          
Defined Benefit Plan Disclosure [Line Items]          
Number of employees covered | employee         1,600
International Association Of Machinists And Aerospace Workers          
Defined Benefit Plan Disclosure [Line Items]          
Number of employees covered | employee         3,400
UPS/IBT Plan          
Defined Benefit Plan Disclosure [Line Items]          
Actuarial gain (loss)       $ 6,400  
Reduction of the liability for coordinating benefits       5,100  
Gain from other updated actuarial assumptions       1,300  
Benefit from basis point increase in discount rate       $ 1,600  
Basis point increase       0.72%  
Asset loss resulting from actual asset returns       $ 300  
Basis points below expected return       2.20%  
Actuarial gain recorded in accumulated other comprehensive income       $ 3,100  
Pre-tax actuarial gain       3,300  
Actuarial gain, after tax       2,500  
Defined Benefit Pension Plan          
Defined Benefit Plan Disclosure [Line Items]          
Multi-employer Plans, Withdrawal Obligation, Fair Value Disclosure       966 $ 1,000
Defined Benefit Pension Plan | Central States Pension Fund          
Defined Benefit Plan Disclosure [Line Items]          
Payment of withdrawal liability   $ 6,100      
Pension liability         5,500
Defined Benefit Pension Plan | Long term debt          
Defined Benefit Plan Disclosure [Line Items]          
Multiemployer Plans, Withdrawal Obligation, Present Value       832 837
Defined Benefit Pension Plan | Other current liabilities          
Defined Benefit Plan Disclosure [Line Items]          
Multiemployer Plans, Withdrawal Obligation, Present Value       8 $ 7
Defined Benefit Pension Plan | U.S. Pension Benefits          
Defined Benefit Plan Disclosure [Line Items]          
Amount contributed to company- sponsored benefit plans       96  
U.S. Postretirement Medical Benefits | U.S. Pension Benefits          
Defined Benefit Plan Disclosure [Line Items]          
Amount contributed to company- sponsored benefit plans       235  
Estimated future employer contributions to defined benefit plan, current fiscal year       $ 21,000